Field of the Invention
The present invention relates to a belt conveyance apparatus used in an image forming apparatus such as a copier using an electrophotography process or an electrostatic recording process, a printer, and a facsimile, and an image forming apparatus including the belt conveyance apparatus.
Description of the Related Art
An image forming apparatus using an electrophotography process or an electrostatic recording process, for example, typically includes a belt conveyance apparatus including an endless belt (hereinafter, may be simply referred to as a “belt”) supported by a plurality of support rollers in a tensioned state. The belt is used as a carrier that carries and conveys a toner image or a recording medium on which a toner image is formed. Examples of the carrier that carries and conveys a toner image include a belt-shaped electrophotographic sensitive member (photosensitive belt) and an intermediate transfer member (intermediate transfer belt) configured to carry and convey a toner image transferred from a photoconductor to transfer the toner image onto a recording medium. Examples of the carrier that carries and conveys a recording medium on which a toner image is formed include a recording medium carrier (conveyance belt) configured to carry and convey a recording medium to which the toner image is transferred from the photoconductor.
An example of the image forming apparatus using an electrophotography process, which includes an intermediate transfer belt, is further described. In general, the intermediate transfer belt configured to be supported by a plurality of support rollers in a tensioned state and rotated (conveyed) may be displaced toward one end in the width direction, which is a direction substantially perpendicular to a conveyance direction, during the rotation. This problem is called “belt deviation (meandering)”. The belt deviation may be caused by factors, such as a low outer diameter accuracy of each support roller and low relative alignment accuracy between the support rollers.
As a measure to solve the problem of the belt deviation, Japanese Patent Laid-Open No. 2002-2999 discloses a technique in which at least one of support rollers is tilted against the other support rollers to move the intermediate transfer belt in a direction opposite to the direction of displacement in the width direction of the intermediate transfer belt.
However, when the steering roller is tilted on a predetermined trajectory as described in Japanese Patent Laid-Open No. 2002-2999, the tilting may destroy the parallel relationship between the steering roller and the other support rollers in the conveyance direction of the intermediate transfer belt. This may cause a stretched surface of the intermediate transfer belt to have a difference in tension in the width direction of the intermediate transfer belt at a position adjacent to a portion wound around the steering roller. Thus, in particular, the stretched surface of the intermediate transfer belt between the steering roller and the support roller (upstream roller), which is positioned adjacent to and upstream of the steering roller in the conveyance direction of the intermediate transfer belt, is readily waved. The wave typically extends radially from a high-tensioned portion of the stretched surface, which is close to the steering roller, toward an upstream side of the intermediate transfer belt in the conveyance direction of the intermediate transfer belt.
If the intermediate transfer belt is waved while traveling, the wave generally disappears at the portion of the intermediate transfer belt to be wound around the steering roller. However, if the wave protrudes such that the height of the wave is larger than the width of the wave, the intermediate transfer belt may be buckled at the portion to be wound around the steering roller. As a result, the intermediate transfer belt may have a crease. If the intermediate transfer belt has a crease, an output image may have a crease, resulting in an image defect. In addition, once the intermediate transfer belt has a crease, the crease is unlikely to be readily smoothed out.